Identification and Characteristics
The dipper is related to wrens and thrushes. Its plump, slate-gray body is 5 to 8 inches long, and it has a brownish head. A thick undercoating of down is enhanced by a large preen gland that secretes oil to waterproof its plumage. A thin, transparent third eyelid, called a nictitating membrane, causes the bird's dark eyes to flash whit when it blinks, allowing it to see underwater. Its short beak is straight and tapered. A moveable flap over the nostrils closes when it dives.
Feeding Behavior
Inhabiting a linear territory along streams, the dipper flies fast and low, rarely deviating from over the watercourse, sometimes plunging beneath the water to resurface upstream. It flits around waterfalls and often perches on rocks adjacent to cascades or riffles, bobbing down and up--hence the name "dipper." It often will forage in the shallows, dipping its head underwater to feed, or it may float like a loon before slipping beneath the surface. Underwater, it "flies" upstream using the current to stay submerged and upright, sometimes gripping the bottom with its strong feet while probing with its beak into crevices. It flips over rocks to catch aquatic insects, nymphs, snails, worms and even small fish and fish eggs.
Mating and Nesting
Nesting takes place May through July. A dome-shaped nest with an arched side entrance is made of moss, mud and grass, and built near fast-moving water on the stream bank or cliff, or concealed upon a creviced rock. Proximity to a waterfall or cascade keeps the nest moist and green. A normal clutch of two to six white eggs is incubated by the female. They hatch in 15 to 17 days and are fledged in another 20 to 25 days. The male helps feed the chicks.
Range and Observation
Usually found singly, the dipper lives in mountainous or cool coastal regions from northern Alaska and the Aleutian Islands through the Canadian Rockies and American west, touching the Black Hills, then south to Mexico and Costa Rica. A year-long resident, dippers are an indicator species in that they cannot exist in polluted or silt-laden waters. If a stream freezes over, dippers move downstream to find open water. Its song, even in the dead of winter, and its "dipping" atop rocks, plus its whirring flight and incessant feeding, make it easy to spot. Dippers tolerate human presence--but stay still.
